1. Field of the Invention
The present invention relates to a torque measuring apparatus for which cleaning operations can easily be performed for removing oil mist or the like attached onto signal receiving units adapted to receive optical signals from a rotor.
2. Description of the Related Art
A torque measuring apparatus is arranged between a rotating shaft at a drive end and a rotating shaft at a load end to measure rotational torque without contact with these shafts. In one application, the torque measuring apparatus is used to measure rotational torque between a measuring roller and a brake mechanism in a chassis dynamo adopted to be rotated by the wheel of an automobile (see, e.g., Japanese Patent Application Laid-Open No. 2002-22566).
FIG. 1 is a front view of a conventional torque measuring apparatus, while FIG. 2 is a partial cross sectional side view of the conventional torque measuring apparatus.
As shown in FIGS. 1 and 2, a conventional torque measuring apparatus 50 is constructed from a rotor 51 arranged between a drive-side shaft 91 and a load-side shaft 93, and a fixed body 55 fixed to the outside of the rotor 51, and is attached between the drive-side shaft 91 and the load-side shaft 93. The rotor 51 is integrated with a drive-side flange portion 52 attached to a flange 92 of the drive-side shaft 91, a load-side flange portion 54 attached to the flange 94 of the load-side shaft 93, and a hollow body portion 53 between the drive-side flange portion 52 and the load-side flange portion 54, and the fixed body 55 is constructed from an annular portion 56 provided on the outside of the load-side flange portion 54 and a chassis 57 to which the annular portion 56 is fixed via a fixture portion 58.
A primary coil 87 is provided in the annular portion 56 arranged on the outside of the load-side flange portion 54, and a secondary coil 88 is provided around the outer periphery of the load-side flange portion 54, the primary coil 87 and secondary coil 88 forming a rotary transformer 89 to supply power to the rotor 51.
In a hollow portion 59 of the hollow body portion 53, a strain gauge torque detection unit 61 is provided, a plurality of light emitting elements 67a to 67n for emitting light or optical signals based on the output from a torque detection unit 61 are provided around the outer periphery of the load-side flange portion 54, an optical fiber 31 for receiving the optical signals from the light emitting elements 67a to 67n is arranged alongside the primary coil 87 in the annular portion 56, and at the end portion of the optical fiber 71 an optical signal conversion unit (not shown) for conversion to electrical signals is provided.
Consequently, the torque measuring apparatus 50, when the drive-side shaft 91 rotates and drives, detects the output from the torque detection unit 61 via the light emitting elements 67a to 67n and the optical fiber 31, by means of the optical signal conversion unit, whereby the rotational torque is detected.
As described above, although the conventional torque measuring apparatus 50 is interposed between the drive-side shaft 91 and the load-side shaft 93 and can measure torque without being in contact with its rotating portion, the torque measuring apparatus are installed in many cases in the environment in which oil mist or the like is generated.
As a result, the oil mist or the like attached onto the light receiving fiber 71 as a light receiving portion may cause damage to measuring precision and abnormal conditions such as impossibility of measurement, so that the light receiving fiber 71 must be cleaned. However, the cleaning operation is rather difficult because the light receiving optical fiber 31 is arranged inside the annular portion 56, leading to a demand for improvement in the cleaning operation.